RESEARCH METHODS IN SPORTS AND CLINICAL BIOMECHANICS

Within sports and health sciences, the biomechanical study of human movement has many purposes, including rehabilitation, injury prevention and performance analysis. While in clinical biomechanics the main goal is to determine if a motion is physiological or if it differs from normal values, in the sports context the aim is finding the movement determinants that allows an athlete to perform at the highest possible level. Research in movement analysis is nowadays supported by multi-camera stereophotogrammetric systems, used to reconstruct three-dimensional body landmarks coordinates from video images. These allow the collection of quantitative information about the mechanics of the musculo-skeletal system during the execution of a motor task. In particular, the following quantities will be considered: the kinematics of the whole-body centre of mass (CoM); the relative movement between adjacent bones (joint kinematics); body segment energy variation and muscular work. The current thesis contains the main experimental projects of my doctoral research activity. Many performance analyses were based on the estimation of the kinematics of the body CoM, whose reliability was demonstrated with a reduced marker set, which is desirable when dealing with complex movements. Inspecting CoM kinematics gives the researcher a complete view of the athletes’ movements, with a insight on balance and motor control: we found that expert karateka, who are supposed to possess superior balance abilities, perform the same fighting sequence with a lower CoM as compared with amateur practitioners. We also found that the strategy adopted by young soccer players to be faster in a slalom dribbling task consists in the optimization of CoM path throughout the course, i.e. in a more sophisticated motor control. The inspection of joint kinematics allows to assess the functioning of kinetic chains, i.e. proximal-to-distal linkage between segments, and to understand the phases of complex multi-segmental techniques: in soccer pass-kick we identified laterality-driven differences between the preferred and non-preferred side. Kinematic curves, as well as gait cycle parameters like step width, length or cadence, helped in identifying locomotion issues in a patient wearing a knee endoprosthesis. An emerging and stimulating challenge in motion analysis is the extraction of distinct features from the large amount of available kinematic data: two are symmetry and variability. Symmetry indexes were applied to assess the effects of a physiotherapy intervention on a prosthetic patient, while a novel repeatability index was developed for mandibular joint motion. Additionally, multivariate statistical techniques like the Principal Components Analysis allowed for the identification of abnormal gait patterns in urologic patients, as well as for the extraction of fundamental motor modules from complex sports skill in soccer and elite karate athletes.